Prevent browser crash resulting from misbehaving WebVR renderer requesting multiple VSyncs.

chrome/browser/android/vr_shell/vr_shell_gl.cc

Index: chrome/browser/android/vr_shell/vr_shell_gl.cc
diff --git a/chrome/browser/android/vr_shell/vr_shell_gl.cc b/chrome/browser/android/vr_shell/vr_shell_gl.cc
index 73afb7117c0ac2266959055deaf971b4f109f303..d78088568e784b92a11f6a0905cef706d6fb4a3f 100644
--- a/chrome/browser/android/vr_shell/vr_shell_gl.cc
+++ b/chrome/browser/android/vr_shell/vr_shell_gl.cc
@@ -175,7 +175,9 @@ VrShellGl::VrShellGl(
 VrShellGl::~VrShellGl() {
   vsync_task_.Cancel();
   if (!callback_.is_null()) {
-    base::ResetAndReturn(&callback_).Run(nullptr, base::TimeDelta(), -1);
+    base::ResetAndReturn(&callback_)
+        .Run(nullptr, base::TimeDelta(), -1,
+             device::mojom::VRVSyncProvider::Error::ERROR_TRY_AGAIN);

[bajones, 2017/02/23 17:21:22]

Could you clarify this? If the VSyncProvider is being destroyed why are we
telling Blink to try again?

[mthiesse, 2017/02/23 18:11:58]

Added comments.

   }
   if (binding_.is_bound()) {
     main_thread_task_runner_->PostTask(FROM_HERE, base::Bind(
@@ -1091,6 +1093,8 @@ void VrShellGl::OnRequest(device::mojom::VRVSyncProviderRequest request) {
 void VrShellGl::GetVSync(const GetVSyncCallback& callback) {
   if (!pending_vsync_) {
     if (!callback_.is_null()) {
+      callback.Run(nullptr, base::TimeDelta(), -1,
+                   device::mojom::VRVSyncProvider::Error::ERROR_BAD_REQUEST);
       mojo::ReportBadMessage("Requested VSync before waiting for response to "
           "previous request.");
       return;
@@ -1135,7 +1139,8 @@ void VrShellGl::SendVSync(base::TimeDelta time,
 
   webvr_head_pose_[frame_index % kPoseRingBufferSize] = head_mat;
 
-  callback.Run(VrShell::VRPosePtrFromGvrPose(head_mat), time, frame_index);
+  callback.Run(VrShell::VRPosePtrFromGvrPose(head_mat), time, frame_index,
+               device::mojom::VRVSyncProvider::Error::ERROR_NONE);
 }
 
 void VrShellGl::ResetPose() {